Low-valent titanium and zirconium reagents in situ prepared from metallocene dichlorides (Cp2MCl2: M = Ti, Zr) and magnesium powder activated by 1,2-dibromoethane smoothly reacted with allyl propargyl ethers to afford 3-methylenetetrahydrofurans in good yields. It is noteworthy that the Cp2Zr- and Cp2Ti-mediated cyclizations proceed with inverse stereoselectivity.
由茂
金属二
氯化物(Cp 2 MCl 2:M = Ti,Zr)和被
1,2-二溴乙烷活化的
镁粉原位制备的低价
钛和
锆试剂与烯丙基
炔丙基醚平稳反应,以高收率得到3-亚甲基
四氢呋喃。值得注意的是,Cp 2 Zr和Cp 2 Ti介导的环化反应的立体选择性反演。